Looking back on all of humanity's successes in space, it can be easy to forget that many of our accomplishments have been built on the sacrifices of other creatures. Here are ten animals who played an indispensable role in paving the inter-planetary way to space.

Top image: French cats in spacesuits.

10. Fruit flies
If we're going to talk animals in space, it makes sense to start with the first — and that title goes to none other than the unassuming fruit fly. A number of them were launched aboard an American V2 rocket on February 20, 1947 to explore the effects of radiation on space-faring organisms.

The astro-flies' rocket was launched to an altitude of 68 miles (the United States and international definitions of "the edge of space" are 50 miles and 62 miles, respectively) before returning to Earth, at which point the flies were recovered alive.

9. Dogs
It would be remiss of us, of course, to leave dogs off this list — and seeing as we just got done talking about the first animal in space, it bears mentioning that the first animal in Earth's orbit was, in fact, a dog.

Laika, pictured here, was a stray-turned-Soviet space dog launched aboard Sputnik 2 on November 3, 1957. Unfortunately, Laika was also the first animal to perish in space, dying due to overheating just a few hours after entering orbit — a fact that has haunted some Soviet scientists ever since:

"Work with animals is a source of suffering to all of us," said former Soviet scientist Oleg Gazenko (one of the scientists responsible for sending Laika into space) at a Moscow News conference in 1998. "We treat them like babies who cannot speak. The more time passes, the more I'm sorry about it. We shouldn't have done it... We did not learn enough from this mission to justify the death of the dog."

8. Cats
But the Soviets weren't the only ones to send strays skyward; in 1963, France had every intention of sending a stray named Felix into space. Felix, however, had other plans, and flew the coop prior to the October 18th launch date. Felix was replaced by a female stray dubbed Félicette (featured here looking very stepford-kitty, probably on account of the electrodes that were implanted in her brain to monitor her in-flight neural impulses).

Unlike Laika, Félicette never entered Earth orbit. Her mission was to simply travel into space and descend to Earth by parachute, and lasted less than 15 minutes. That said, Félicette was also recovered alive.

7. Spiders
The first arachnids in space were European garden spiders named Arabella and Anita. The pair were launched on July 28, 1973 aboard the Saturn IB rocket, in the US's second manned mission to Skylab.

Once in orbit, scientists monitored Anita and Arabella to see what effect being in Earth's orbit would have on their web-spinning abilities. Pictured here is the first spider web to be spun in space, produced by Arabella. All things considered, she did a pretty bang-up job (although the thickness of the silk was found to vary significantly throughout the web — a feature not encountered in Earth-spun spider structures).

6. Bullfrogs
In 1970, NASA launched its Orbiting Frog Otolith spacecraft, with the primary goal of gathering information on the effects of weightlessness on the brain's perception of gravity and acceleration in space (your otolith is part of the system your inner ear uses to keep you balanced).

Data gathered from electrodes implanted in the bullfrogs' thoracic cavities and vestibular nerves (your vestibular system plays a critical role in your sense of balance) revealed that the initial periods of weightlessness led to abnormal vestibular responses, but that these changes eventually reverted to normal, suggesting that the bullfrogs ultimately acclimated to their zero-g environment.

5. The Russian tortoise
The first tortoises in space were a pair of Russian tortoises that were launched, fittingly enough, by the Soviet Union in 1968. What makes their flight especially noteworthy, however, is that it was actually a circumlunar one; the Zond 5 spacecraft on which they were stowed away actually flew around the Moon and back to Earth, making planetfall in the Indian Ocean. That means these little badasses were two of the first animals to ever enter deep space (joining the pair on its epic journey were wine flies and mealworms… but let's be honest, the real heroes here are the tortoises).

And best of all? They survived the trip. What I can't find information on is whether they're still alive today — but seeing as Russian tortoises have life spans of about 75 years, it's certainly possible.

4. Rabbits
The first rabbit in space, like the first tortoise, was also launched on a Soviet mission. Marfusha, pictured here looking plucky alongside two of her in-flight companions, was launched on a high-altitude test flight on July 2, 1959, aboard an R2-A rocket. All three animals were recovered alive.

Featured here is a series of Haiku tributes to Marfusha, "The People's Bunny," by musician John Talley-Jones. Apart from the slight jab at Laika, they're pretty awesome.

3. Newts
The Pleurodeles waltl species of newt, pictured here, has been studied in space on at least six missions, and on some of the most interesting, as well. In 1985, the USSR's Bion 7 mission launched ten newts with amputated forelimbs into space for the purpose of studying an organism's potential for recovery from injury in space (newts were a good organismal model because they possess the ability to grow entirely new limbs). Incredibly, the newts were found to regenerate significantly faster in space than they do here on Earth.

2. Chimpanzees
The history of space travel has seen numerous chimpanzees launched to space, but the very first was Ham, pictured here strapped into his biopack couch before being launched in an American Mercury capsule on January 31, 1961.

Ham's mission was different from that of just about every other organism on this list because he was actually trained to operate levers during his mission, and his ability to do so efficiently while in flight demonstrated the feasibility of sending a person to space.

1. Water Bears
Water bears are also known as tardigrades, but why would you ever go by tardigrade when you could go by "water bear"? These water-dwelling microorganisms have eight legs, measure less than 1.5 millimeters in length, and are, all things considered, probably the hardiest creatures we've ever sent into space.

Case in point: in September, 2007, water bears were launched into low Earth orbit on the ESA's FOTON-M3 mission where they were exposed to the intense radiation and vacuum of space FOR TEN DAYS. When the water bears were returned to Earth and rehydrated, 68% of them were revived — in the process becoming the first animals to survive the vacuum of space.